Certain undesirable physiological manifestations, such as acne vulgaris, seborrhea, female hirsutism, androgenic alopecia which includes female and male pattern baldness, and benign prostatic hyperplasia, are the result of hyperandrogenic stimulation caused by an excessive accumulation of testosterone ("T") or similar androgenic hormones in the metabolic system. Early attempts to provide a chemotherapeutic agent to counter the undesirable results of hyperandrogenicity resulted in the discovery of several steroidal antiandrogens having undesirable hormonal activities of their own. The estrogens, for example, not only counteract the effect of the androgens but have a feminizing effect as well. Non-steroidal antiandrogens have also been developed, for example, 4'-nitro-3'-trifluoromethyl-isobutyranilide. See Neri, et al., Endocrinol. 1972, 91 (2). However, these products, though devoid of hormonal effects, compete with all natural androgens for receptor sites, and hence have a tendency to feminize a male host or the male fetus of a female host and/or initiate feed-back effects which would cause hyperstimulation of the testes.
The principal mediator of androgenic activity in some target organs, e.g. the prostate, is 5.alpha.-dihydrotestosterone ("DHT"), formed locally in the target organ by the action of testosterone-5.alpha.-reductase. Inhibitors of testosterone-5.alpha.-reductase will serve to prevent or lessen symptoms of hyperandrogenic stimulation in these organs. See especially U.S. Pat. No. 4,377,584 assigned to Merck & Co., Inc., issued Mar. 22, 1983. It is now known that a second 5.alpha.-reductase isozyme exists, which interacts with skin tissues, especially in scalp tissues. See, e.g., G. Harris, et al., Proc. Natl. Acad. Sci. USA, Vol. 89, pp. 10787-10791 (November 1992). The isozyme that principally interacts in skin tissues is conventionally designated as 5.alpha.-reductase 1 (or 5.alpha.-reductase type 1), while the isozyme that principally interacts within the prostatic tissues is designated as 5.alpha.-reductase 2 (or 5.alpha.-reductase type 2).
Finasteride (17.beta.-(N-tert-butylcarbamoyl)-4-aza-5.alpha.-androst-1-ene-3-one), which is marketed by Merck & Co., Inc. under the tradename PROSCAR.RTM., is an inhibitor of 5.alpha.-reductase 2 and is known to be useful for the treatment of hyperandrogenic conditions. See e.g., U.S. Pat. No. 4,760,071. Finasteride is currently marketed in the United States and worldwide for the treatment of benign prostatic hyperplasia. Finasteride's utility in the treatment of androgenic alopecia and prostatic carcinoma is also disclosed in the following documents: EP 0 285,382, published Oct. 5, 1988; EP 0 285 383, published Oct. 5, 1988; Canadian Patent no. 1,302,277; and Canadian Patent no. 1,302,276. The specific dosages exemplified in the above-noted disclosures varied from 5 to 2000 mg per patient per day.
In the treatment of androgenic alopecia, which includes both female and male pattern baldness, and other hyperandrogenic conditions, it would be desirable to administer the lowest dosage possible of a pharmaceutical compound to a patient and still maintain therapeutic efficacy. Applicants have surprisingly and unexpectedly discovered that a low daily dosage of a 50.alpha.-reductase 2 inhibitor is particularly useful in the treatment of androgenic alopecia. Furthermore, a low daily dosage of a 5.alpha.-reductase 2 inhibitor may also be particularly useful in the treatment of the hyperandrogenic conditions of acne vulgaris, seborrhea, female hirsutism, and polycystic ovary syndrome.